Several music pieces from this game were recycled for others games from the same musicians:
The mission 1 music was recycled and remixed in "Gun Force II" (Stage 2 part 1).
The mission 2 music contains a synth solo (after 32 seconds) which was performed with a sax in "Metal Slug 2 - Super Vehicle-001/II" (mission 3).
The mission 3 music was recycled and remixed with electric guitar in "Metal Slug 3" (mission 1, underwater way).
The mission 3 music was also recycled and remixed in "Gun Force II" (Stage 2 part 2).
The mission 4 music was recycled and remixed in "Gun Force II" (stage 1).